Bushing for oil-filled electrical apparatus



Nov. 2, 1948.

A. MEYERHANS BUSHING FOR OIL-FILLED ELECTRICAL APPARATUS Filed NOV. 14, 1945 Patented Nov. 2, 1948 BUSHING FOR OIL-FILLED ELECTRICAL APPARATUS August Meyerhans, land, assignm- Bieden, near Baden, Switzerto Aktlengeseilshaft Brown,

Boveri & Cie, Baden, Switzerland Application November 14, 1945, Serial No. 628,526

- In Switzerland November 16, 1944 2 Claims. (Cl. 174-31) Bushings for leading in or bringing out conductors from the tanks of electrical apparatus filled with oil or some other insulating material,

for instance transformer tanks, increase in size as the voltage increases, so that apparatus equipped with such bushings may no longer be able to be transported by rail owing to the loading gauge being exceeded.

The present invention concerns a bushing for oil-tilled electrical apparatus, particularly transformers, where the aforementioned disadvantage is overcome by the insulation at the leading-in point being covered by an insulator shed which projects out of the oil tank and is surrounded by an insulating cover filled with oil and dimensioned for the flash-over distance in air.

A constructional example of the invention is explained by means of the accompanying drawing where a bushing is shown in longitudinal section, all details which are not directly concerned with the invention'having been omitted for the sake of clearness.

In the figure a indicates the cover of a transformer tank through which the conduc or 1) passes in an insulated manner. The conductor 1) leads to the winding of a transformer, not shown in the drawing. At the point where the insulated conductor 1) passes through the cover of the tank an insulator tube is introduced on which the paper insulation d is wound, this paper insulation d having multiple flanged ends produced by the edges of the paper layers being slit open and bent over. The insulation 11 together with the metal body e surrounding it, is enclosed by the insulator shed j which projects out of the tank a. An annular metallic and conductive disc 70 arranged concentric with the opening in tank a and having an inner diameter less than that of the tank opening surrounds the shed ,f and is-fastened to the outside wall of the tank by bolts 1 with a washer m of sealing material interposed between the two ,to render the joint leak-proof. Shed I at its lower end terminates in a flanged portion f extending outwardly beneath the disc k and is secured at the flange along with annular plates 12 and o by means of bolts p to the underside of disc It. An oil sealing washer r1 is placed between the upper surface of flange 1" and the underside of disc is to prevent air from leaking into the interior of tank a at this point. At the top end of ..the insulating shed 1 there is a metal terminal 57 to which the bare end of the conductor b and the lead his connected. An insulator tube i placed over the insulator shed I and secured to the disc is by means of an annular 2 clamping member 1' engaging the flange i and bolts 8 which extend through member 1" into disc k. The space between the insulators f and i is filled with oil, and a sealing washer t is clamped between the bottom end face of insulator i and disc is to prevent oil leakage. Insulator i is dimensioned for the flash-over distance in air and provided with a protective spark gap. The

conductive sleeve e is conductiv'ely connected by means of the plate 0 which contacts it circumferentially and bolts p to the disc k; sleeve e thus serves as a disc screen and also reduces the electrical field at the foot of the insulator 'i.

Bushings of the kind described above can easily be shortened to facilitate transportation by re moving the insulator i. The short inner insulator shed f shuts off the easily damaged insulation of the conductor from the atmosphere, so that it can remain under oil during transport. This bushing does not require any lower cover in order to retain the oil, so that its lower part is very short. These reductions in height are a great advantage for large transformers which have to comply with railway loading gauges.

If for any reason, for instance due to external influence. insulator i should burst, the amount of oil which escapes is very small and the damage which occurs will only be very slight especially when the insulator shed j, which is then surrounded by air, withstands the normal operating voltage (phase voltage) until disconnection occurs.

During transportation the insulator shed f can be protected by a metal hood not illustrated which is fastened to the disc in place of the insulator 1.

Due to the insulator shed f be ng fixed to the lower side of the disc k, it is possible to keep the external diameterof the bushing small.

I claim:

1. In a bushing structure for leading a conductor through an open ng in an o l fill ed tank for connection to electrical apparatus such as transformers and the like enclosed within the tank, in combination, an annular disc secured to the outside of the tank adjacent to and concentric with the tank opening, the inner diameter of said disc being less than that of the tank opening, an outer hollow insulator secured to said disc and extending outwardly of the tank, a conductor extending through the tank opening, a multi-layered insulating sheath having spread end flanges surrounding the conductor at the tank opening, a bell-shaped insulating shed surrounding a portion of said insulating sheath and extending through said disc into said outer insulator. said shed being provided with a sealed terminal extending through its upper wall and a flanged portion at its lower end extending beneath and adjacent to said disc, and means securing the flanged portion of said shed to said disc.

2. In a bushing structure for leading a conductor through an opening in an oil filled conductive tank for connection to electrical apba ratus such as transformers and the like enclosed within the tank, in combination, an annular conductive disc secured to the outside of the tank adjacent to and concentric with the tank open ing and in conductive relation with the tank, the inner diameter of said disc being less than that oi" the tank opening, on outer hoiiow insuiator secured to said disc and extending outwardly from the tank, a conductor extending through the tank opening, a muiti-ieyered insulating sheath having spread end flanges surrounding the conductor at the tank opening, a conductive sleeve overlaid on the oumrmost layer oi said insulating sheath, e heILshaped insulating shed surrounding a portion of said insulating sheath and sieeve and which extends through said disc oat 4 into said outer insulator, said shed being provided with a sealed terminal extending through its upper wall and a flanged portion at its lower end extending beneath and adjacent to said disc. an annular conductive member surrounding and in contact with said conductive sleeve beneath the flanged portion of said shed, and means securing said conductive member and the flanged portion of said shed to said disc, said conductive sleeve being conductively related to said disc through said conductive member.

AUGUST MEYERHANB.

REFERENQJES CITE-ED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

